Amazon has made many improvements to the KF8 reading software over the old mobi/prc.

Really? What are they? The line spacing is smaller, the font sizes are all gratuitously different (making for a disruptive reading experience if you have both KF8 and MOBI books on your device), it *still* can't hyphenate, it somehow manages to be laggier than the Java-based mobi reader (fairly frequently missing page-turns or mixing multiple together, even on a K4 with its hardware page-turn buttons), and publishers can foolishly choose to jam in their chosen (pig-ugly) font and prevent you from changing it to the one you prefer for all your other books. Oh, and the file sizes are larger. None of these things seem at all positive to me.

I mean, if they were rewriting the reading app in a different language they could at least have added hyphenation too. It's not like hyphenation in C hasn't been a solved problem for thirty-odd years at this point.

I hope they at least left the ability to run JavaScript out: I was astonished when ePub added that, has nobody learned anything about the dangers of adding interpreters that can run arbitrary code in totally unexpected places?